Among heritable conditions alone, there are over 100 examples of diseases involving the loss of retinal neurons. For example, glaucoma is one of the leading causes of blindness in the world. Approximately, 2.5 million people in the United States have glaucoma and more than 130,000 people are legally blind from the disease. Glaucoma presents a complex pathology. It is characterized by retinal and optic nerve neuropathies, eventually leading to death of retinal ganglion cells (RGCs) and their axons, as well as the excavation of the optic nerve head. In addition, chronic open angle glaucoma is often associated with elevated intraocular pressure (IOP) resulting from increased resistance to drainage of the aqueous humor. Many types of glaucoma have been described including pigment dispersion syndrome and pseudoexfoliation of the lens which is characterized by the deposition of pigment granules and an aberrant protein, respectively, throughout the anterior segment of the eye.
One potential strategy for treating glaucoma and other types of disorders is to transplant retinal stem cells into the eye of the diseased donor. After transplantation, these retinal stem cells could then differentiate, allowing repair of the diseased eye. Because of the ethical and governmental restrictions on the use of embryonic stem cells, there is a real interest in developing materials and methods involving adult retinal stem cells rather than embryonic retinal stem cells. However, the success of adult retinal stem cell transplantation is dependent on a number of factors.
For example, clinical outcomes for patients undergoing transplantation have traditionally been affected by adverse immune responses provoked by the transplanted cells. Use of autologous cells can minimize or eliminate such adverse reactions. Previously, retinal stem cells have been isolated directly from the retina or retinal pigment epithelium. Performance of this isolation procedure, however, results in partial traumatic injury to these tissues or complete destruction of the retina or retinal pigment epithelium. Hence, using these techniques, it is impossible to harvest retinal stem cells from the intended recipient without partial or complete injury to the eye of the recipient/donor. Accordingly, there is a need to develop methods of isolating retinal stem cells without injury or destruction of the retina or retinal epithelium, thereby allowing the transplantation of autologous retinal stem cells.
Additionally, successful use of adult retinal stem cells lines for transplantation has been impeded by the difficulty in propagating and maintaining adult cell lines. Unlike embryonic stem cells, adult stem cells have a self-limited life span. Therefore, adult stem cells must be used immediately after culturing, making it necessary to have a donor on hand for any successful transplantation procedure. Hence, there is a need to develop methods of growing and maintaining adult retinal stem cells in culture, thereby increasing the bank of donor cells available for transplantation. This invention fulfills these needs and others.